The ribbon burner is a mature low cost technology which is well liked and accepted by multiple industries. For example, ribbon burners have found widespread application in many industrial baking, drying and surface treatment applications.
Ribbon burners conventionally utilize a long, thin slot filled with corrugated metal strips to create a narrow array of short interconnected flames.
Burners are typically operated either fully aerated (fully premixed oxidizer and fuel) or partially aerated (partially premixed oxidizer and fuel). In practice, the typical or common oxidizer media used with conventional burners is air. In such operation, the portion of air used for (partial) combustion that is mixed with the fuel is commonly called “primary air”; the remaining portion of air is commonly called “secondary air”. Fully aerated burners use only primary air; partially aerated burners use both primary air and secondary air.
In combustion processing, the degree of partial aeration is often expressed via what is commonly referred to as the “Primary Equivalence Ratio” or PER. The PER is the primary fuel/(oxidizer or air) ratio divided by the stoichiometric fuel/(oxidizer or air) ratio. The stoichiometric fuel/(oxidizer or air) ratio is the theoretical ratio of fuel to (oxidizer or air) that results in complete combustion with no remaining or left over fuel and no left over (oxidizer or air).
Ribbon burners that are fueled with natural gas and the emissions that are formed or produced thereby have been or are in the process of coming under stricter and stricter regulations in various selected regions of the United States, e.g., California. Consequently, reducing emissions of nitrogen oxides (commonly represented as “NOx” and typically including one or more of NO, NO2, and N2O) is critical to the continued use of ribbon burners.
The development of a lower NOx emission ribbon burner without jeopardizing the simplicity, reliability, and the low cost advantages normally associated with the use of ribbon burners has presented a significant challenge. One attempted approach for reducing NOx in ribbon burners as well as in other partially premixed types of burners has been through the burner utilization of porous or mesh materials rather than corrugated metal strips. Such an approach allows increasing the heat transfer from the combustion process via the radiation mode of operation while also reducing the flame temperature. As a result, such an approach may act to reduce thermal NOx formation. This approach, however, has its shortcomings including power output limitations as well as reduced or lower reliability and durability.
If the NOx emission performance of ribbon burners is not significantly improved within the near term, users of ribbon burners such as in the baking industry and the drying industry, for example, may be forced to replace established, cost effective and reliable ribbon burner technology with some lower NOx emission alternative such as expensive electric alternatives.
Thus, there is a need and a demand ribbon burners and/or a method for operating ribbon burners such that desired NOx emission performance can be realized.